(1) Field of the Invention
The present invention relates generally to torpedo countermeasure devices and, more specifically, to programmable apparatus and methods for emulating torpedo countermeasure devices.
(2) Description of the Prior Art
Torpedo countermeasure (CM) devices are used on ships and submarines to confuse incoming torpedos. Therefore, a need exists for testing U.S. torpedoes with respect to foreign countermeasures to determine the efficacy of U.S. torpedoes when confronted by countermeasures. The current methodology of testing U.S. torpedoes is to use a U.S. countermeasure device that is thought to be representative of a possible foreign CM device, and use this U.S. countermeasure in field tests. However, because prior art U.S. countermeasures may not be the same as various foreign countermeasures, are highly limited in the type of response which may be produced especially with respect to the requirements of emulating foreign countermeasures, and do not have related desirable features for this purpose as discussed below, the testing may not be as complete as may be desired.
The prior art discloses various types of training required by submarines and the development of various types of acoustic devices, but does not provide a solution to the above disclosed problem and does not even appear to recognize this long felt need. Representative patents in this area include the following:
U.S. Pat. No. 2,887,671, issued May 19, 1959, to Burton Frankel et al., discloses an invention pertaining to a sonar device used in the training of sonar operators to acquaint them with the characteristic sounds of a sonar ping returning from a submarine. Claim 1 states: In a sonar device, an elongated hull to be placed underwater and having a forward and an aft transducer for receiving a sonar ping, comparing means mounted in the hull for comparing the time relationship of arrival of a given ping as received by the forward and aft transducers, means connecting the forward and aft transducers to the comparing means, signal generating means connected to the comparing means for generating a signal having a characteristic which is a function of the relationship, and transmitting transducer means mounted on the elongated hull and connected to the signal generating means for transmitting the generated signal.
U.S. Pat. No. 5,394,376, issued Feb. 28, 1995, to Laurence R. Riddle et al, discloses an apparatus for reducing acoustic radiation from an enclosure containing a fluid including one or more vibration sensors in communication with surfaces of the enclosure. The vibration sensors feed signals corresponding to detected vibrations in the surface to a radiation filter. The radiation filter assigns weights to the signals and generates a summation signal which is then input to a control unit, with the summation signal ideally representing only those vibrations that will actually radiate from the enclosure. The control unit uses a reference signal and the summation signal to calculate a cancellation waveform to offset the cause of the detected vibrations. The cancellation signal is input to a fluid displacement unit which applies pressure oscillations to the fluid corresponding to the cancellation waveform.
U.S. Pat. No. 4,184,209, issued Jan. 15, 1980, to Ralph P. Crist, discloses a towed decoy system adapted to be towed from a towing vessel, an electrically powered noisemaker, an electrical tow cable attached to the noisemaker, a depressor vane, a depressor cable connected to the depressor vane and to the towing vessel, and means interconnecting the depressor cable and the electrical tow cable at a point near the depressor vane, the interconnecting means comprising a pair of cable grips respectively attached at one end to adjacent sections of the electrical tow cable and at their other ends to a snatch block movably mounted on the depressor cable thereby providing slack in the electrical tow cable, whereby the noisemaker is towed at a depth not less than that of the point of attachment of the snatch block to the depressor cable.
U.S. Pat. No. 4,025,724, issued May 24, 1977, to Allen R. Davidson, Jr. et al., discloses an array of independent sound cancellation units arranged over a vibrating noise generating surface. Each unit includes an arrangement of acoustic transducers (sensors) positioned adjacent the surface to obtain an electrical average of the local acoustic noise generated by a predetermined zone of the surface. The summed average is changed in phase and gain by an active filter whose output drives an acoustic projector also positioned adjacent the surface and the acoustic output of which sums with the original noise signal in the acoustic far field, thus tending to cancel the noise. In essence, each vibrating surface zone and its associated sound cancellation unit tends to form an acoustic doublet. A signal indicative of the projector output is used as a feedback signal, with appropriate time delays, to cancel the effect of the projected output signal being picked up by the unit's transducers, and to cancel the effect of the output of other projectors of the array.
U.S. Pat. No. 5,033,028, issued Jul. 16, 1991, to Douglas R. Browning, discloses and describes an apparatus and method for overcoming stroke limitations of moving coil reaction-mass vibration dampers, by recovering armature stroke displacement. The coil housing is selectively coupled or de-coupled to the vibrating structure. If, when the armature reaches its travel limit, sufficient damping energy has not been applied to the structure, the coil-housing assembly is decoupled from the structure while the armature is pulsed back to its zero displacement position. The housing then is re-coupled to the surface, having displaced some determinable distance from its previous location relative to the surface. Additional armature movement in the same direction as the previous armature stroke is applied, thereby generating the needed additional damping force. The resetting of the housing to its normal position vis-a-vis the vibrating structure can occur at a selected time in the damping force-generating cycle when reset does not impart an undesired reaction to the vibrating structure. In one implementation, a pair of moving-coil actuators counter-drive the vibrating structure; in another, a multiplicity of additional reaction-mass actuators are used.
U.S. Pat. No. 5,341,343, issued Aug. 23, 1994, to Robert L. Aske, discloses an explosive actuated acoustic device which emits sound to be used in torpedo countermeasures. Numbered devices are delivered over an extended area and sink through the water. The devices are actuated at different times as they sink, to provide sound masking over an extended period of time. The devices also include safety devices which prevent premature actuation from jarring or jolting and from impact with the water.
U.S. Pat. No. 5,117,401, issued May 26, 1992, to Paul L. Feintuch, discloses an active adaptive noise canceller that inserts delays in the weight update logic of an adaptive filter employed by the canceller to make the filter stable. It has been found that there is a great deal of flexibility regarding the selection of the delay values. This insensitivity permits designing the delays in advance and not having to adjust them to different situations as they change, thus no longer requiring a training mode. The canceller dramatically reduces the amount of hardware needed to perform active adaptive noise cancelling, and eliminates the need for the training mode, which in some applications, including automobiles, for example, can be objectionable as the noise sources that are to be suppressed.
The above patents do not address or provide solutions to the problem of testing torpedoes with respect to various types of countermeasures. Consequently, it would be desirable to provide an in-water device that can emulate known characteristics of CM devices, both U.S. and foreign. It would be desirable for such a device to be reusable, either stationary or mobile, and suitable for both in-laboratory and in-water use. Moreover, it would be desirable to provide a system that is totally programmable and can be programmed to intercept and identify a threat waveform, and then respond in a totally programmable manner, including pre-programmed structured signals, broad band noise, narrow band noise, echo repeater mode, swept LFM mode, or any one of several possible randomly generated false alarm modes where the transmission is a modified replica of the intercepted threat waveform. Those skilled in the art will appreciate the present invention that addresses the above and other needs and problems.